1. Field of the Invention
The present invention relates to a polishing apparatus for polishing a workpiece such as a semiconductor wafer to a flat mirror finish, and more particularly to a polishing apparatus having an easy maintenance characteristic.
2. Description of the Related Art
Recent rapid progress in semiconductor device integration demands smaller and smaller wiring patterns or interconnections and also narrower spaces between interconnections which connect active areas. One of the processes available for forming such interconnections is photolithography. Though the photolithographic process can form interconnections that are at most 0.5 .mu.m wide, it requires that surfaces on which pattern images are to be focused by a stepper be as flat as possible because the depth of focus of the optical system is relatively small.
It is therefore necessary to make the surfaces of semiconductor wafers flat for photolithography. One customary way of flattening the surfaces of semiconductor wafers is to polish them with a polishing apparatus, and such a process is called Chemical Mechanical polishing.
FIG. 7 shows one conventional polishing apparatus having a polishing section 100 for polishing semiconductor wafers. The polishing section 100 comprises a turntable 110 having a polishing surface 111 and rotatable about its own axis at a predetermined speed, a top ring 120 for holding a semiconductor wafer to rotate the semiconductor wafer at a predetermined speed and pressing the semiconductor wafer against the polishing surface 111 of the turntable 110 for thereby polishing a surface of the semiconductor wafer, and a dressing tool 130 for dressing the polishing surface 111 to regenerate the polishing surface in contact therewith. The turntable 110, the top ring 120, and the dressing tool 130 are housed in a single chamber 101.
The polishing apparatus also has a cleaning section 140 for conveying the semiconductor wafers and cleaning the semiconductor wafers. The cleaning section 140 comprises two workpiece conveying robots 151, 153 for taking a semiconductor wafer out of a cassette and delivering the semiconductor wafer to the polishing section 100, primary and secondary cleaning devices 161, 163 for cleaning the semiconductor wafer which has been polished, a drying device 170 for drying the semiconductor wafer which has been cleaned, and two workpiece reversing devices 181, 183 for reversing the semiconductor wafer upside down. The workpiece conveying robots 151, 153, the primary and secondary cleaning devices 161, 163, the drying device 170, and the workpiece reversing devices 181, 183 are housed in a single chamber 141.
Certain parts of the top ring 120, a polishing cloth which provides the polishing surface 111 of the turntable 110, and a dressing element such as a dresser brush or a diamond grain layer on the dressing tool 130 are expendable articles or parts that should be replaced with new ones periodically by maintenance operations.
The cleaning devices 161, 163 also have expendable articles including cleaning brushes and sponge elements which are also required to be replaced with new ones periodically by maintenance operations.
The above maintenance operations are not and do not signify service repair activities for repairing the polishing section 100 and the cleaning section 140 in the event of malfunctions or failures, but periodical replacement routines for replacing expendable articles or parts.
Heretofore, the maintenance operations or activities which involve parts replacement have been carried out at three different side faces of the apparatus, i.e., a side face "a" for maintenance such as replacement of the parts of the top ring 120, a side face "b" for maintenance such as replacement of the polishing cloth constituting the polishing surface 111, and a side face "c" for maintenance such as replacement of the dresser brush of the dressing tool 130 and the cleaning brushes of the cleaning devices 161, 163.
Because of these three side faces "a", "b" and "c" involved, it has been necessary to provide respective empty spaces in front of the side faces "a", "b" and "c" to allow approach and access to the side faces "a", "b" and "c" for maintenance such as the replacement of parts. Consequently, any one of these side faces "a", "b" and "c" cannot be positioned closely to other hindering objects such as walls or pillars, with the result that a large installation space has been required for the installation of the polishing apparatus.
When the polishing apparatus is to be maintained or serviced successively at the side faces "a", "b" and "c", the maintenance operator has to move from one side face to another while carrying tools and parts. Therefore, maintenance of the polishing apparatus has been troublesome and time-consuming.
FIG. 8 is a perspective view showing an outer appearance of the conventional polishing apparatus shown in FIG. 7. As shown in FIG. 8, the polishing section 100 and the cleaning section 140 are housed in respective chambers in the form of rectangular parallelepipeds.
The polishing section 100 and the cleaning section 140 have a number of pipes 171, 181 extending from side walls of the chambers for supplying liquid to and discharging liquid from the various units and machines in the polishing section 100 and the cleaning section 140. The pipes 171, 181 extend vertically through a floor 180 into a machinery room (not shown) below the floor 180, and are connected to various devices in the machinery room.
Heretofore, the pipes 171, 181 projecting out of the chambers are randomly located, and cause various problems described below.
Since the pipes 171, 181 project from the side walls of the chambers, they present obstacles when the polishing section 100 and the cleaning section 140 are maintained, or transported for installation thereof. When the pipes 171, 181 are damaged or broken by collision with operators or other objects, they give rise to safety problems.
The operation of installation of the polishing apparatus on the floor 180 is troublesome and time-consuming because the floor 180 has to be drilled to make holes for insertion of the pipes 171, 181.
The pipes 171, 181 project from the side walls of the chambers into passages around the chambers and tend to obstruct operators walking along the passages. Therefore, the pipes 171, 181 cause the polishing apparatus to take up a greater installation space than would be required by their physical size. In addition, the pipes 171, 181 are not sightly to external view.